Watch Back Case Opener Screw Wrench Repair Remover Tool This High Quality toll is designed to open and close screw back watch cases. Will open Large majority of watch backs that are screw fitting Comes in a Hard plastic Storage box.18 Tips if 6 different sets Knurled handle for firm grip.Adjustable Thumb Wheel. Works with Round, Square, Hexagonal and serrated backs.Maximum Jaw opening 35mm